Characteristics of 73 studies that reported the use of Robson's classification.

*3 letters, 1 unpublished manuscript**1 study with 8 South American countries, 1 study with 9 countries including Oceania, North America and Europe***Commentaries and letters#World Bank Income Group Classification http://data.worldbank.org/about/country-classifications/country-and-lending-groups#Low_income. Out of 83 as some studies had multiple countries.♦Coverage is defined as the number of women included in the classification as a percentage of the total number of women delivered during the study period.